In a post on X, the FBI’s Phoenix office said anyone with “firsthand knowledge” of Guthrie’s whereabouts should contact the FBI tip line at 1-800-CALL-FBI.
Until now, the reward has been $200,000 – $100,000 offered by the FBI and another $100,000 through Tucson Crime Stoppers.
Guthrie was reported missing around midday on 1 February after she did not show up for church services.
The Pima County Sheriff’s Office has said they believe she was “taken from the home against her will, possibly in the middle of the night and that includes possible kidnapping or abduction”.
The family has made several public pleas for her safe return, and asked for proof that she is alive. Nancy Guthrie has difficulty walking, has a pacemaker and needs daily medication for a heart condition, authorities have said.
Investigators have released images of the prime suspect – a man captured on Nancy Guthrie’s Nest doorbell camera.